Hoping to get a good night's rest? Then you may want to stay away from tablet screens before bedtime. A new study by Harvard Medical School researchers shows that using an iPad before bed suppresses the body's production of melatonin, a sleep-regulating hormone, making it harder to fall asleep and reducing sleep quality.
During the two-week inpatient study, twelve participants read digital books on an iPad for four hours before bedtime each night for five consecutive nights. This was repeated with printed books. The order was randomized with some reading on the iPad first and others reading the printed book first. Participants reading on the iPad took longer to fall asleep, were less sleepy in the evening and spent less time in REM sleep. They had reduced secretion of melatonin, a hormone that normally rises in the evening and plays a role in inducing sleepiness. Additionally, iPad readers had a delayed circadian rhythm, indicated by melatonin levels, of more than an hour. Participants who read on the iPad were less sleepy before bedtime but were sleepier and less alert the following morning after eight hours of sleep. Although iPads were used in this study, researchers also measured other devices that emit blue light, including eReaders, laptops, cell phones and LED monitors.
You can check out the full study here. Apparently, subjects had to spend four hours reading (on either iPads or paper books) from 6 PM to 10 PM. Designated sleep hours were 10 PM to 6 AM.
Other studies have shown that, in the evening, cooler (6500K) light is a greater impediment to melatonin production than warmer (3000K) light. Tablet displays tend to be calibrated for a color temperature of around 6500K, which could explain the results of the Harvard Medical School study.
The solution may be to go back to paper books and board games during evening hours. Or it could be something like f.lux, which automatically lowers the screen's color temperature after sunset. Too bad f.lux doesn't work on non-jailbroken iPads.